Bug 5424

Summary: Deadlock in XGetExtensionVersion() when XInitThreads() is called before
Product: xorg Reporter: Felix Hädicke <felixhaedicke>
Component: Lib/XiAssignee: Xorg Project Team <xorg-team>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: critical    
Priority: high CC: gregm
Version: 6.9.0   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Port of XFree's patch (for X.org 6.9) none

Description Felix Hädicke 2005-12-26 11:25:04 UTC 
There is a bug that calling XGetExtensionVersion() after XInitThreads() always   
causes a deadlock.   
   
I do not really use XGetExtensionVersion() myself, but I found a deadlock in  
the Qt library in the QApplication constructor, and this seems to be caused by   
XGetExtensionVersion() and happens only if XInitThreads() is called before.   
According to this forum posting (which is probably the same bug):   
http://www.qt-forum.org/thread.php?threadid=14988&sid=e99b9990f5fbbec62dc5e650d36b160f&hilight=XInitThreads   
this did not happen in XFree 4.3 - but I have not tried this myself, so I  
cannot confirm this. The bug can be reproduced with X.org 6.8.2 and X.org 6.9  
with the following test program:  
   
Simple test program test.c to reproduce this bug:     
---------------------------------------------     
     
#include <X11/Xlib.h>      
#include <X11/extensions/XInput.h>      
      
int main(int argc, char * argv[]) {      
        XInitThreads();      
        Display * dpy = XOpenDisplay(NULL);      
        XGetExtensionVersion (dpy, "XInputExtension");      
        return 0;      
}      
     
---------------------------------------------     
     
gcc -I/usr/include/X11 -L/usr/X11R6/lib -lXs11 -lXi -lpthread test.c -o test
Comment 2 Felix Hädicke 2005-12-26 11:33:47 UTC 
*** Bug 5423 has been marked as a duplicate of this bug. ***
Comment 3 Felix Hädicke 2005-12-26 12:06:51 UTC 
I found this in the XFree bug list: 
 
http://bugs.xfree86.org/show_bug.cgi?id=260 
 
They have a working bugfix.
Comment 4 Felix Hädicke 2005-12-26 12:29:53 UTC 
Created attachment 4163 [details] [review]
Port of XFree's patch (for X.org 6.9)

This patch works for me (hope there are no license issues due to license
differences between X.org and XFree86)
Comment 5 Daniel Stone 2007-02-27 01:29:32 UTC 
Sorry about the phenomenal bug spam, guys.  Adding xorg-team@ to the QA contact so bugs don't get lost in future.
Comment 6 Alan Coopersmith 2007-05-21 17:07:00 UTC 
*** Bug 1413 has been marked as a duplicate of this bug. ***
Comment 7 Jeremy Huddleston Sequoia 2011-09-24 23:00:16 UTC 
Current libXi uses _XiGetExtensionVersion which doesn't lock.  The reported thread fixes this in pretty much the same way as the current git, so I'm marking as fixed.

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